It is a common practice to deliver fluids such as medications to a patient intravenously by means of a pumping device such as a peristaltic pump. Such pumps are useful because they can deliver the medication in a highly controlled fashion, and because they do so without coming in contact with the medication. The fluid is moved through a flexible IV tube by pressing a pumping member against the tube sufficiently to occlude the tube, and then moving the pumping member along the tube to advance the fluid which is trapped downstream of the occlusion.
After the pumping member completes a stroke, a second pumping member repeats the process by occluding the tube and moving a second captured quantity of fluid along behind the first. The distance between occlusions and the speed of movement of the pumping members can be precisely controlled to effectively control the rate of infusion of the fluid into the patient. The IV tube is at all times occluded by one of the pumping members, thereby preventing "free flow" of fluid, by means other than the action of the pumping members.
It is common for the peristaltic pumping mechanism to be housed in a housing with a hinged door. The tube through which the fluid is to be moved is placed in contact with the pumping mechanism inside the door, with the ends of the tubing typically extending out the top and bottom of the door opening. As the door is shut over the tube, a platen on the inside of the door presses against the IV tube to provide a backing surface against which the pumping members can occlude the tube.
This arrangement of the IV tube relative to the pumping mechanism requires that there be some means for preventing flow in the tube when the door is open. Otherwise, during the process of setting up or dismantling the infusion apparatus, unwanted flow of fluid could occur in the IV tube. This could result in the uncontrolled infusion of medication into the patient under the influence of the static head in the tube, or blood from the patient could flow back into the IV tube. Known devices for preventing unwanted flow in the tube include manual clamps separate from the infusion pump, and automatic occluding devices mounted on the pump.
The manual devices require some manipulation skill on the part of the attending technician, and there is always the chance that the technician will forget to properly time the occlusion of the tube relative to the opening of the door on the pumping device. Furthermore, the door may be accidentally opened, resulting in free flow in the tube.
The known automatic devices mounted on the infusion pump are not uniformly reliable in timing the occlusion and release of the tube with the disengagement and engagement, respectively, of the pumping members. Typically, the action of opening the door is relied on to initiate the occlusion of the IV tube, and the action of closing the door is relied on to initiate the release of the IV tube. Therefore, at least momentary free flow of fluid can occur in some of these devices, or very accurate and repetitive alignment of the operative surfaces of the occlusion mechanism can be required. Some known devices also will allow the occluding device in the pump to be independently disengaged, whether by accident or on purpose, without the door being closed. This obviously results in the free flow of fluid.
Therefore, the object of the present invention is to provide an apparatus which will automatically and positively occlude an IV tube before the pumping mechanism is disengaged from the tube. A further object of the present invention is to provide an apparatus which will automatically and positively maintain the IV tube in an occluded state until after the pumping mechanism is engaged with the tube. A still further object is to provide an apparatus which will reliably occlude the IV tube, which is inexpensive to manufacture and easy to use.